Your guess is as good as anyone else's. Of course there are no technical difficulties (hell, the D2 could run Linux or whatever), it's just a political decision on Cowon's account. So my guess is - no, it will not get ViVA support, since that would cannibalize S9 (and upcoming players) sales.

Cowon could have given the D2+ ViVA support from the get-go, but they didn't. So I wouldn't count on it being added in future firmware upgrades.

I highly doubt it, the D2 wass released in 2007 wasn't it? the D2+ is basically just a little upgrade to give D2 sales a bit of a boost. They're gonna save the biggest and best features (like viva) for newer players, like S9 or anything in the future. Think of it this way, if you had a product, two years old, that had already gone through whatever price cuts it could, and you want to phase it out of your manufacturing, then you wouldn't give it the most attention via firmware upgrades. Especially in the "new features" department. you want everyone to look at the new player you're rolling out and say "wow that has so much my old player doesn't!" this will make them want to buy the new player more. If they gave the D2 the viva bbe then that's one less feature the new players will have over it.